So do ADCOMs see email and username on your app? How does this affect their decision if you have an immature username or email?
If you're at a point in your life where you're applying to medical school, perhaps it's time to grow up and make yourself a more mature e-mail address.
This is stupid. Make a new, professional gmail address. Every admissions office will use your email and if you send update letters, deans and adcoms will see it as well.